There are occasions in medical practice where it is desirable to check the sterility or other properties of a liquid stored in a pouch before that liquid is administered to a patient or otherwise used. Examples are blood and blood components such as serum and platelets. The US blood industry association, the American Association of Blood Banks (AABB), an association that is globally recognized, recently updated the technical requirements for blood collection, storage and testing and has included a new pre-transfusion QC requirement that will go into effect in March 2004. The new QC test requirement involves testing stored platelets for evidence of bacteria. If bacteria are detected in a unit (ie, a pouch) of platelets, that unit will not be eligible for transfusion. In order to perform the necessary tests, multiple samples of platelets are usually extracted from the platelet container into respective sample phials. In some cases samples from multiple pouches are mixed and then tested. However, there is serious danger that the sampling procedure itself can introduce bacteria into the pouch liquid.
The pouches usually have attached plastic filling tubes that have been heat-sealed. To take a sample, a sharp hollow steel needle attached to a syringe can be inserted into the filling tube and some of the liquid withdrawn before the needle pulled out of the tube. Desirably, the filling tube can be heat-sealed again between the pouch and the puncture point. Some pouches are provided with ‘needleless ports’, which have septums that can be penetrated by blunt cannulae attached to syringes. In either case, bacteria can be introduced into the pouch during the sampling process and/or by subsequent entry through the puncture site. The use of a blunt cannular with a needleless port not risks introducing bacterial into the pouch but it normally does not allow for subsequent heat-sealing to isolate the port. Of course, collecting samples by using a needle to puncture the thin wall of the pouch itself offers the worst alternative because of the likelihood that, after withdrawal of the needle, the thin wall of the pouch will not seal sufficiently to prevent the ingress of bacteria through the puncture site.